# Thread: Math question... kinda abstract

1. ## Math question... kinda abstract

Do all expressions have a domain? Or is it just for functions?

2. yes all expressions have a domain.

3. Why?

4. oh, whoops should have explained...

well, functions are merely shorthand notations for longer expressions, and since functions have domains (be they the whole complex plane, only real parts, subsets of it due to singularities, etc), expressions do as well.

5. A function is a mapping of one set on another set, like f:A->B. The first set is the domain, so each function has a domain.

6. Originally posted by doubleanti
oh, whoops should have explained...

well, functions are merely shorthand notations for longer expressions, and since functions have domains (be they the whole complex plane, only real parts, subsets of it due to singularities, etc), expressions do as well.
Woah, woah, hold on there! You sure that isn't a quote from star trek?

I feel incredibly stupid whenever da talks, moreso than usual.

7. "The whole complex plane" would mean all numbers, real, imaginary, and complex (combination of the two)

"Only real parts" would mean part of the real numbers (you know...the ones represented by your fingers and toes.

By "singularities," I believe he means holes, such as the one found in y=(x^2)/(x-2) at x=2.

So...no star trek, just some combination of pre-calc and calc class.

8. "Only real parts" would mean part of the real numbers (you know...the ones represented by your fingers and toes.
Or parts thereof.